What types of diseases and problems does an abdominal/pelvic ct show? does it detect different types of cancer?

It may detect many: Ct is an imaging tool. It detects abnormal anatomy or changes on normal appearance of internal organs. Whether the cause of those changes is cancer or not , its decided by taking the biopsy of the abnormally looking structures. Example: mass at the head of the pancreas. Sometimes, ct can detect abnormal bleeding or inflammation.